A standard thermostatically regulated valve such as described in German patent 3,530,812 filed August 29, 1985 by J. Kostorz has hot- and cold-water inlets connected to respective valve seats whose other sides open into an outlet compartment from which tempered water flows. A double valve body is displaceable in one direction to increase the flow from one of the inlets to the outlet compartment and decrease the flow from the other inlet and is oppositely movable for the opposite effect. This valve body can be moved by axially displacing an externally displaceable stem, and is also provided with a temperature-sensitive element in the outlet compartment that ca change length to move the valve element and keep it at the setting it is originally put into. Thus once a given mixed-water temperature is set, the temperature-sensitive element will automatically move the valve bodies in response, for instance, to varying supply temperatures to keep the output temperature steady.
The manual setting of such a valve is typically by means of a simple knob threaded on the rotatable and axially displaceable valve stem. Thus as the temperature is adjusted, the knob is screwed axially along the stem. This change in axial as well as angular position is disadvantageous in that it makes it impossible for a pointer on the valve to align accurately with a scale fixed relative to the valve stem.
German patent 1,164,779 of F. Bayer describes a thermostatic valve where the rotary control knob does not move axially as the valve is adjusted. The mechanism of this valve, however, does not otherwise correspond to the above-described valve with an axially movable stem so that this type of knob cannot be adapted to it.